Drill bit



Um. E7, 1968 W, D ELENBURG 3,436,6l7

DRILL BIT Filed Aug, 22, 1966 ff @y/@gjm irre/@New6 United States Patent3,416,617 DRILL BIT Wayland D. Elenburg, Wichita Falls, Tex., assignorto Walker-Neer Manufacturing Company, Inc., Wichita Falls, Tex., acorporation of Texas Filed Aug. 22, 1966, Ser. No. 574,054 6 Claims.(Cl. 175-339) ABSTRACT OF THE DISCLOSURE A drill bit adapted for usewith a continuous dual passage drill pipe and including fluid ducts fordirecting flow from around the inner drill pipe onto the cuttingmembers. A skirt around the cutting members greatly restricts flow tothe outside of the bit so that almost all return ow is up through theinner pipe. A radial collar further restricts upward flow.

This invention relates to a drill bit, and, more particularly, to adrill bit adapted for use with dual concentric drill pipe adapted fordrilling with reverse circulation.

Well drilling operations with reverse circulation have increasedappreciably with the development of concentric, dual passage drill pipeas shown in Homer I. Henderson, U.S. Patent No. 3,208,539, dated Sept.28, 1965. However, even greater advantages can be realized in reversecirculation, if the amount of circulating fluid released to the holeannulus were kept to a minimum. It is a particular advantage of dualpassage drill pipe in that drilling fluid is circulated through conduitsof fixed, uniform cross-section producing superior cutting recovery andproviding better cooling and lubrication. This is not possible whencirculating through the hole annulus, and in the event of cave-ins orfractured formations, a considerable amount of fluid may be lost.Moreover, the mere circulation of fluid into the formation underpressure can, itself, influence the undesirable fracturing ofsub-surface formations.

It is, therefore, an object of this invention to provide a drill bitwhich, during operation, restricts substantially all flow of circulatingfluid to within the dual passage drill pipe, preventing excessive flowinto the formation.

It is a further object of this invention to provide a drill bit with arelatively high velocity return ow passage and with minimum interferenceto the free movement of cuttings.

It is a further object of this invention to provide a cone rock bit withreverse circulation flow directed across the cones.

In carrying out this invention, I provide a cone-type rock bit having agenerally cylindrical -body of substantially uniform diameter from topto bottom. The upper portion of the hollow body is threaded, preferablyinternally for attachment to the outer pipe of a dual pipe string and aninner return tube is threaded to an internal shoulder near the lower endof the hit, so that the inner tube is coaxially disposed with the bitbody, with a space around providing a passage for downward ow. A seriesof rock cones are carried at the lower end of the bit for cuttingthrough the formation and flow passages or nozzles are cut through theinternal shoulder so that ow is directed against the cones. Two owpassages are directed against each one, each along a chord of thecircular cross-section to wash away cuttings and sediment clinging tothem. At the lower end of the bit body, the outer surface is extendeddownwardly to form a skirt or barrier around the bit body which,together with the cones themselves, substantially confine circulationfrom the nozzles to the formation directly under the bit, and then toreturn through the inner tube. A radial collar around the bit furtherrestricts flow outside of the bit to an amount just sufficient tolubricate rice the drill pipe. A similar tubular extension depends fromthe inner tube so that cuttings are quickly contained within theconfined cross-section for increased velocity and superior containment.

Other objects and advantages of this invention will become apparent fromthe description following when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a schematic illustration of a well drilling system embodyingfeatures of this invention;

FIG. 2 is a vertical section view of the lower end of the drill pipestring and drill bit embodying features of this invention; and

FIG. 3 is a section view taken along line 3-3 of FIG.

Referring now to FIG. l, my well drilling system 10 includes an outerdrill pipe 12 through which a drilling fluid is introduced at 14 fromany suitable source (not shown), an inner cutting recovery tube 16through which the fluid returns with cuttings C entrained therein, and agooseneck 18 through which the cuttings C are delivered to a suitablescreen 20 for separation. If drilling mud is used as the circulatingmedium, it is then delivered to a conventional mud pit 22 afterdepositing the cuttings. However, it is to be understood that the systemcan also employ air, Wateraerated fluid and other fluid media.

At the lower end of the drill pipe 12 is a rock bit 24 which is providedwith a depending skirt or barrier 26 partially embracing the cones 28and extending between them in order to restrict flow into the wellannulus W. Just above the bit cutting cones, a radial extension 30around the bit body sharply restricts upward flow through the holeannulus W minimizing loss to formations as invasion formations.Preferably, the radial extension 30 is interrupted at arcuate intervalsin order to permit just enough fluid to lubricate the pipe. Preferably,the radial extension or collar is provided with cutting edges at theinterruptions 32 in order to perform reaming functions.

Referring now to FIG. 2, the drill Vbit is shown in greater detail and,in its preferred form, comprises a cylindrical hollow body 34 which isinternally threaded at 36 for connection with a conventional pincoupling of a drill pipe and, toward its lower end, is formed with aninternal shoulder 38 through which fluid ducts or nozzles 40 are formed.The internal shoulder 38 is preferably stepped inward at 42 and providedwith suitable securing means, such as threads 43, to receive and retaina thin-walled cutting chip return tube 44 is susbtantially flush withthe central opening 46 through the internal shoulder. Hence, the centralbit opening 46 and return tube 44 provide a smooth uniform flow passagewhich minimizes entrapment of cuttings and enables controlled flow rate.As seen best in FIGS. 2 and 3, the cutting cones 28 are mounted ontapered extensions 48 depending from the lower end of the bit tbody 34,and are retained thereon, as by means of journals 50. Intermediate thecones 28 downwardly extending skirt or barriers 26 from a continuationof the lower edge of the tapered bosses to restrict flow from thenozzles 38 outward of the bit body so that substantially all flow isconfined to within the fixed cross-section of the bit body 34.

Also depending from the bit body around the central opening areadditional arcuate extensions 49 which bring the return tube 44 close tothe bit so that the cuttings C are introduced to high velocity flow ofthe restricted, uniform cross-section immediately after being reversedfrom the formation.

As shown in FIGS. 2 and 3, the annular collar or dam 30 almostcompletely blocks the hole annulus W against upward ow which the cuttingedges 32 ream out the hole, although enough flow is permitted throughthe water ways at 32 in order to lubricate between the drill pipe 12 andthe bore hole wall W. As shown in FIG. 2, the annular reaming collar maybe provided on an intermediate pipe section or sub 52 which, in turn, isthreaded to the lower end of a dual passage drill pipe string. However,if desired, the reaming collar may be carried on the bit body 34 itself.

In any event, a thin-walled return tube 16 is secured within the outerpipe by suitable means (not shown) Aso as to be relatively fixedaxially, i.e., supported therein, and it is held in spaced coaxialrelationship by means of ribs 54 or the like which are welded to theinner tube 16. Where a separate sub 52 is employed for the reamingcollar 30, the return tube 44 carried by the bit 34 is of sufiicientlength to extend completely through the intermediate sub 52 so as to bereceived by the complementary sleeve 56 carried at the lower end of thedrill pipe inner tube 16, the telescopic connection being sealed bysuitable means such as an O-ring 58. Even where a separate sub 52 isemployed, the sub and drill bit may be broken from the drill pipe 12 asaunit.

Referring now to FIG. 3, it will be noted that each cone cutter 28 isopposed by two nozzles 40, each of which is directed along a nearlytangential chord of the circular cross-section of the cone so as toimpinge thereon without undue flow restriction and washcircumferentially around it and axially inward toward the drill bitcentral return entry 46, thus keeping the cones clean, especially insofter formations.

While in FIG. 2 it appears that the bore wall W snugly surrounds the bitbody, this is not intended to illustrate a precise relationship and, inpractice, some clearance will result. However, the skirt will provide acontinuous bearing surface for distribution of bearing loadings duringrotation of the bit body, and for substantial elimination of impact wearas occurs in the event of separate, spaced cone-carrying bit shanks. Theresult is a substantial reduction of shirt-tail wear that plaguesconventional rock bits.

While this invention has been described in connection with the preferredembodiment thereof, it is obvious that modifications and changes thereinmay be made without departing from the spirit and scope of thisinvention as defined by the claims appended hereto.

Having described my invention, I claim:

1. For use in well drilling apparatus comprising a continuous dual pipestring with concentric inner and outer pipes forming an annular downwardow passage between them and a central return flow passage, aformation-cutting drill bit comprising:

a cylindrical tubular body of substantially uniform external diameterfrom top to bottom,

threaded means on the upper portion of said tubular body,

means forming an internal shoulder at the lower end of said body,

a cylindrical tube mounted on said shoulder to form therewith a centralflow passage coaxially disposed within said body,

coupling means on the upper end of said cylindrical tube adapting it fortelescopic connection with complementary means on the inner pipe of adual pipe string,

cutting members carried at the lower end of said body and adapted toengage and cut the bottom of a bore hole in response to rotation of saidbody,

fluid ducts through said shoulder directed against said cutting members,

a tubular skirt depending from the lower end of said body between saidcutting members and embracing said fluid ducts, the lower edge of saidskirt being spaced slightly above the bottom-engaging portion of saidcutting member to restrict greatly flow of uid therefrom radiallyoutward of said tubular body, and

a radial collar around said cylindrical body to restrict further the owcapacity in said bore hole outward of said tubular body.

2. The combination defined by claim 1 wherein:

said lower edge of the skirt embraces said cutting member.

3. The combination defined by claim 2 wherein:

said skirt forms a complete cylinder embracing said cutting member.

4. The combination defined by claim 1, including:

means forming limited iiow passages through said collar.

5. The combination defined by claim 1 wherein said cylindrical drill bitbody is threaded internally for connection to complementary couplingmeans on a drill pipe.

6. The combination defined by claim 1 wherein said cutting memberscomprise cones with formation penetrating members thereon, and arerotatably mounted in said cylindrical body, and there are two iluidducts through said shoulder directed on each of said cones.

References Cited UNITED STATES PATENTS 1,256,694 2/1918 Hughes 175-3391,263,802 4/1918 Reed 175-340 1,582,332 4/1926 Brutus 175--339 X2,093,633 9/1937 Catland 175-339 X 3,208,539 9/ 1965 Henderson 175--69 X3,292,719 12/ 1966 Schumacher 175-339 NILE C. BYERS, I R., PrimaryExaminer.

